Turnstiles are known to differ from revolving doors in that they do not have full-surface door wing leaves, but cross wings consisting of a plurality of bar-shaped or plate-shaped members arranged in one plane one on top of another, which members are arranged at vertically spaced locations from each other, so that they are able to pass through a stationary blocking grid delimiting the blocking sector.
The cross wings can be driven manually or by a motor. However, it is required in any case that the cross wings be moved into a defined starting position and be blocked there after one passage.
To enable such turnstiles to be used as security revolving doors, it is necessary to provide, besides an electrical or electronic control unit with peripheral monitoring devices, e.g., card readers, space sensors, etc., a blocking device with electrically controllable blocking members, which blocking device makes it possible to block the turnstile against rotation optionally in one rotation direction and/or in the other rotation direction in defined angular positions, and it also must be ensured at the same time that the rotation blocking acts in one direction only and the turnstile can be turned back into its starting position in the opposite direction. In addition, depending on the particular application, it must be possible to impose specifically defined characteristics on the blocking device in the case of power failure, so that the turnstile is, for example, freely rotatable or blocked in both directions, or is blocked in one direction only. In any case, it must be guaranteed that a person located in the passage sector cannot be locked in by the rotation blocking of the turnstile.